A fuel injection pump provided in a diesel engine has traditionally been well-known. Further, an electromagnetic spill valve provided in the fuel injection pump has also been well-known. To the electromagnetic spill valve, drive current whose current waveform is shaped by a control device is applied, and a fuel injection amount is adjusted by releasing pressurized fuel with opening/closing of the valve (e.g., see Patent Literature 1; hereinafter PTL 1).
Traditionally, the control device includes a full automatic mode and a manual mode as means for shaping the current waveform of the drive current of the electromagnetic spill valve. In the full automatic mode, a valve-close (maximum lift) timing of the electromagnetic spill valve is detected, and an optimum current waveform of the drive current is formed based on the detected maximum lift timing. In the manual mode, only the current waveform of the preset drive current is formed.
However, in cases where the diesel engine is operated in a cold state by using fuel oil C having a relatively high viscosity as the fuel, and the current waveform of the drive current of the electromagnetic spill valve is formed in the full automatic mode, a phenomenon in which the drive current collapses may take place. This phenomenon is thought to be caused by the following reason. Namely, a high viscosity of the fuel oil C during the cold state slows down the behavior of the electromagnetic spill valve, and the maximum lift timing cannot be detected.
Further, when such a phenomenon takes place in the diesel engine, it is confirmed that the normal waveform of the flowing current is not restored even if the engine is operated for a long time in a steady state (i.e., in the state where the fuel viscosity is sufficiently low).